Perhaps no issue is more nerve-wracking today than same-sex marriage. It’s a magnet for controversy, evoking strong reactions from those on either side of the debate. But beneath all the fiery passion and rhetoric, there are real arguments to evaluate. In this article, we’ll examine the 10 most common ones made in favor of same-sex marriage, many of which you’ve probably heard before. By pointing out the flaws, we’ll show how each argument ultimately comes up short.

However, before we begin, let’s note a few things. First, this article concerns civil marriage — marriage as defined and promoted by the state. It doesn’t deal with the Church’s sacramental understanding, although the two often overlap. Second, the responses to the arguments are emphatically nonreligious. They don’t depend on any sacred text or divine revelation. They’re based on reason, philosophy, biology and history. Third, this article only refutes arguments in favor of same-sex marriage. It doesn’t touch upon the many positive arguments supporting traditional marriage.

One more note: This is not an attack on people with same-sex attractions. All people, regardless of sexual orientation, deserve to be treated with dignity and respect. Instead, this article is a rational look at whether civil marriage, an institution that touches all people and cultures, should be redefined.

1. Marriage has evolved throughout history, so it can change again.

Different cultures have treated marriage differently. Some promoted arranged marriages. Others tied marriage to dowries. Still others saw marriage as a political relationship through which they could forge family alliances.

But all these variations still embraced the fundamental, unchanging essence of marriage. They still saw it, in general, as a public, lifelong partnership between one man and one woman for the sake of generating and raising children.

This understanding predates any government or religion. It’s a pre-political, pre-religious institution evident even in cultures that had no law or faith to promote it.

Yet, even supposing the essence of marriage could change, would that mean it should? We know from other areas of life such as medical research and nuclear physics that just because you can do something doesn’t mean you ought. After all, such action may not be ethical or serve the common good. Even if this argument had historical basis, it would not necessarily be a good reason to change the meaning of marriage.

2. Same-sex marriage is primarily about equality.

This argument is emotionally powerful since we all have deep, innate longings for fairness and equality. Moreover, history has given us many failures in this area, including women banned from voting and African-Americans denied equal civil rights. The question, of course, is whether same-sex couples are denied equality by not being allowed to marry each other.

To answer that, we first must understand equality. Equality is not equivalency. It does not mean treating every person or every group in exactly the same way. To use an analogy, men and women have equal rights, but because they significantly differ they require separate restrooms. Equality means treating similar things similarly, but not things that are fundamentally different.

Second, there are really two issues here: the equality of different people and the equality of different relationships. The current marriage laws already treat all people equally. Any unmarried man and unmarried woman can marry each other, regardless of their sexual orientation; the law is neutral with respect to orientation just as it ignores race and religion.

The real question is whether same-sex relationships differ significantly from opposite-sex relationships, and the answer is yes. The largest difference is that same-sex couples cannot produce children, nor ensure a child’s basic right to be raised by his mother and father. These facts alone mean we’re talking about two very different types of relationships. It’s wrong, therefore, to assume the state should necessarily treat them as if they were the same.

Same-sex marriage advocates may argue that it’s discriminatory to favor heterosexual spouses over homosexual couples. With all of the benefits flowing from marriage, this unfairly endorses one set of relationships over another. But if the state endorsed same-sex marriage, it would then be favoring gay “spouses” over unmarried heterosexual couples. The argument runs both ways and is ultimately self-defeating.

3. Everyone has the right to marry whomever he or she loves.

Though catchy, few people truly believe this slogan. Most of us acknowledge there should be at least some limitations on marriage for social or health reasons. For example, a man can’t marry a young child or a close relative. And if a man is truly in love with two different women, he’s legally not allowed to marry both of them, even if both agree to such an arrangement.

So, the real question here is not whether marriage should be limited, but how. To answer that, we must determine why the government even bothers with marriage. It’s not to validate two people who love each other, nice as that is. It’s because marriage between one man and one woman is likely to result in a family with children. Since the government is deeply interested in the propagation and stabilization of society, it promotes and regulates this specific type of relationship above all others.

To put it simply, in the eyes of the state, marriage is not about adults; it’s about children. Claiming a “right to marry whomever I love” ignores the true emphasis of marriage.

Notice that nobody is telling anyone whom he or she can or cannot love. Every person, regardless of orientation, is free to enter into private romantic relationships with whomever he or she chooses. But there is no general right to have any relationship recognized as marriage by the government.

4. Same-sex marriage won’t affect you, so what’s the big deal?

Since marriage is a relationship between two individuals, what effect would it have on the rest of us? At first glance, it sounds like a good question, but a deeper look reveals that since marriage is a public institution, redefining it would affect all of society.

First, it would weaken marriage. After same-sex marriage was legislated in Spain in 2005, marriage rates plummeted. The same happened in the Netherlands. Redefining marriage obscures its meaning and purpose, thereby discouraging people from taking it seriously.

Second, it would affect education and parenting. After same-sex marriage was legalized in Canada, the Toronto School Board implemented a curriculum promoting homosexuality and denouncing “heterosexism.” They also produced posters titled “Love Knows No Gender,” which depicted both homosexual and polygamous relationships as equivalent to marriage. Despite parents’ objections, the board decreed that they had no right to remove their children from such instruction. This and many similar cases confirm that when marriage is redefined, the new definition is forced on children, regardless of their parents’ desires.Third, redefining marriage would threaten moral and religious liberty. This is already evident in our own country. In Massachusetts and Washington, D.C., for instance, Catholic Charities can no longer provide charitable adoption services based on new definitions of marriage. Elsewhere, Canadian Bishop Frederick Henry was investigated by the Alberta Human Rights Commission for simply explaining the Catholic Church’s teaching on homosexuality in a newspaper column. Examples like this show how redefining marriage threatens religious freedom.

5. Same-sex marriage will not lead to other redefinitions.

When marriage revolves around procreation, it makes sense to restrict it to one man and one woman. That’s the only relationship capable of producing children. But if we redefine marriage as simply a loving, romantic union between committed adults, what principled reason would we have for rejecting polygamist or polyamorous — that is, multiple-person — relationships as marriages?

Thomas Peters, cultural director at the National Organization for Marriage, doesn’t see one. “Once you sever the institution of marriage from its biological roots, there is little reason to cease redefining it to suit the demands of various interest groups,” Peters said.

This isn’t just scaremongering or a hypothetical slippery slope. These aftereffects have already been observed in countries that have legalized same-sex marriage. For example, in Brazil and the Netherlands, three-way relationships were recently granted the full rights of marriage. After marriage was redefined in Canada, a polygamist man launched legal action to have his relationships recognized by law. Even in our own country, the California Legislature passed a bill to legalize families of three or more parents.

Procreation is the main reason civil marriage is limited to two people. When sexual love replaces children as the primary purpose of marriage, restricting it to just two people no longer makes sense.

This argument concerns two relatively rare situations: younger infertile couples and elderly couples. If marriage is about children, why does the state allow the first group to marry? The reason is that while we know every same-sex couple is infertile, we don’t generally know that about opposite-sex couples.

Some suggest forcing every engaged couple to undergo mandatory fertility testing before marriage. But this would be outrageous. Besides being prohibitively expensive, it would also be an egregious invasion of privacy, all to detect an extremely small minority of couples.

Another problem is that infertility is often misdiagnosed. Fertile couples may be wrongly denied marriage under such a scenario. This is never the case for same-sex couples, who cannot produce children together.

But why does the government allow elderly couples to marry? It’s true that most elderly couples cannot reproduce (though women as old as 70 have been known to give birth). However, these marriages are so rare that it’s simply not worth the effort to restrict them. Also, elderly marriages still feature the right combination of man and woman needed to make children. Thus they provide a healthy model for the rest of society, and are still capable of offering children a home with a mother and a father.

7. Children will not be affected since there is no difference between same-sex parents and opposite-sex parents.

This argument was most famously stated in 2005 when the American Psychological Association (APA) wrote that “not a single study has found children of lesbian or gay parents to be disadvantaged in any significant respect relative to children of heterosexual parents.”

However, several recent studies have put that claim to rest. In June, LSU scholar Loren Marks published a peer-reviewed paper in Social Science Research. It examined the 59 studies that the APA relied on for its briefing. Marks discovered that not one of the studies used a large, random, representative sample of lesbian or gay parents and their children. Several used extremely small “convenience” samples, recruiting participants through advertisements or word of mouth, and many failed to even include a control group. Furthermore, the studies did not track the children over time and were largely based on interviews with parents about the upbringing of their own children — a virtual guarantee of biased results.

One month later, Texas sociologist Mark Regnerus released a comprehensive study titled “How Different Are the Adult Children of Parents Who Have Same-Sex Relationships?” His research used a large, random and national sample and its scope was unprecedented among prior work in this field. Contrary to the APA, Regnerus found that for a majority of outcomes, children raised by parents with same-sex relationships drastically underperformed children raised in a household with married, biological parents.

He quickly noted that his study didn’t necessarily show that same-sex couples are bad parents, but that it did definitively put to rest the claim that there are “no differences” among parenting combinations.

8. Opposition to same-sex marriage is based on bigotry, homophobia and religious hatred.

These accusations are not so much an argument for same-sex marriage as personal attacks designed to shut down real dialogue. Let’s look at each one.

First, bigotry. A quick visit to Facebook, Twitter or any online comment box confirms that for many people, support for traditional marriage is tantamount to bigotry.

So, is the charge accurate? Well, the definition of bigotry is “unwilling to tolerate opinions different than your own.” However, tolerating opinions does not require enshrining them through law. One can tolerate advocates of same-sex marriage, and seriously engage the idea, while still rejecting it for compelling reasons.

Second, homophobia. This refers to a fear of homosexuality, and the assumption is that people who oppose same-sex marriage do so because they’re irrationally afraid. But as this article shows, there are many good reasons to oppose same-sex marriage that have nothing to do with fear. Branding someone “homophobic” is typically used to end rational discussion.

Third, religious hatred. Some people disagree with same-sex marriage solely for religious reasons. But, again, as this article demonstrates, one can disagree for other reasons, without appealing to the Bible, divine revelation or any religious authority. You don’t need religious teachings to understand, analyze and discuss the purpose of marriage or its effects on the common good.

If these accusations were all true, it would mean that the overwhelming majority of people throughout time — who by and large supported traditional marriage — would likewise be homophobic, intolerant bigots. That would include the most profound thinkers in many different traditions: Socrates, Plato, Aristotle, Musonius Rufus, Xenophanes, Plutarch, St. Thomas Aquinas, Immanuel Kant and Mahatma Gandhi. Most people would reject such an absurdity.

9. The struggle for same-sex marriage is just like the civil rights movement of the 1960s.

The suggestion here is that sex is similar to race, and therefore denying marriage for either reason is wrong. The problem, however, is that interracial marriage and same-sex marriage are significantly different.

For instance, nothing prevents interracial couples from fulfilling the basic essence of marriage — a public, lifelong relationship ordered toward procreation. Because of this, the anti-miscegenation laws of the 1960s were wrong to discriminate against interracial couples. Yet same-sex couples are not biologically ordered toward procreation and, therefore, cannot fulfill the basic requirements of marriage.

It’s important to note that African-Americans, who have the most poignant memories of marital discrimination, generally disagree that preventing interracial marriage is like banning same-sex marriage. For example, when Californians voted on Proposition 8, a state amendment defining marriage as between one man and one woman, some 70 percent of African-Americans voted in favor.

According to Peters, “Likening same-sex marriage to interracial marriage is puzzling and offensive to most African-Americans, who are shocked at such a comparison.”

10. Same-sex marriage is inevitable, so we should stand on the right side of history.

On Nov. 6, voters in three states — Maine, Maryland and Washington — voted against marriage as it has traditionally been understood. In Minnesota, voters rejected a measure to amend the state constitution to define marriage as between one man and one woman. Many advocates of same-sex marriage considered this a sign that the marriage tides are turning. But is that true? And if so, how does that shift impact the case for same-sex marriage?

First, if the tide is in fact turning, it’s still little more than a ripple. The states that voted in November to redefine marriage did so with slim margins, none garnering more than 53 percent of the vote. The tiny victories were despite record-breaking funding advantages, sitting governors campaigning for same-sex marriage and strong support among the media.

Before these four aberrations, 32 states had voted on the definition of marriage. Each and every time they voted to affirm marriage as the union of one man and one woman. Of the six states that recognized same-sex marriage before the November election, none arrived there through a vote by the people. Each redefinition was imposed by state legislatures and courts. Overall, Americans remain strongly in favor of traditional marriage. Most polls show roughly two-thirds of the country wants to keep marriage as it is.

Yet, even if the tides have recently shifted, that does not make arguments in its favor any more persuasive. We don’t look to other moral issues and say, “Well, people are eventually going to accept it, so we might as well get in line.” We shouldn’t do that for same-sex marriage, either.

Brandon Vogt is a Catholic writer and speaker who blogs at BrandonVogt.com. He is also the author of “The Church and New Media: Blogging Converts, Online Activists, and Bishops Who Tweet” (OSV, $13.95), which you can find atwww.churchandnewmedia.com. He writes from Casselberry, Fla.